"""
Application configuration via pydantic-settings.
All config is loaded from environment variables with sensible defaults.
"""
import os
from pydantic_settings import BaseSettings
from functools import lru_cache


class Settings(BaseSettings):
    # ── App ──────────────────────────────────────────────
    APP_NAME: str = "Document AI Analyst"
    SECRET_KEY: str = "change-me-in-production-please"
    DEBUG: bool = False
    ENVIRONMENT: str = "development"
    ALLOWED_ORIGINS: str = "http://localhost:3000,http://localhost:7860"

    # ── Database ─────────────────────────────────────────
    DATABASE_URL: str = "sqlite:///./data/app.db"

    # ── Auth ─────────────────────────────────────────────
    JWT_ALGORITHM: str = "HS256"
    JWT_ACCESS_EXPIRY_MINUTES: int = 15
    JWT_REFRESH_EXPIRY_DAYS: int = 7
    GOOGLE_CLIENT_ID: str = ""
    HF_CLIENT_ID: str = ""
    HF_CLIENT_SECRET: str = ""
    HF_REDIRECT_URI: str = ""
    FRONTEND_URL: str = "http://localhost:3000"

    # Google Drive background sync
    DRIVE_SYNC_ENABLED: bool = False
    DRIVE_SYNC_INTERVAL_MINUTES: int = 60
    GOOGLE_SERVICE_ACCOUNT_FILE: str = ""

    # Celery / Redis background processing
    CELERY_BROKER_URL: str = "redis://localhost:6379/0"
    CELERY_RESULT_BACKEND: str = "redis://localhost:6379/1"
    CELERY_TASK_TRACK_STARTED: bool = True

    # ── File Upload ──────────────────────────────────────
    UPLOAD_DIR: str = "./data/uploads"
    MAX_UPLOAD_SIZE_MB: int = 20
    ALLOWED_EXTENSIONS: set = {"pdf", "docx", "txt", "md"}
    ALLOWED_MIME_TYPES: dict = {
        ".pdf": ["application/pdf"],
        ".docx": [
            "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
            "application/zip",
        ],
        ".txt": ["text/plain"],
        ".md": ["text/markdown"],

    }

    # ── RAG Pipeline ─────────────────────────────────────
    CHUNK_SIZE: int = 1000
    CHUNK_OVERLAP: int = 200
    TOP_K_RETRIEVAL: int = 10
    TOP_K_RERANK: int = 5

    # ── Knowledge Graph (GraphRAG) ───────────────────────
    GRAPH_PERSIST_DIR: str = "./data/graphs"
    GRAPH_ENTITY_LABELS: set = {
        "PERSON",
        "ORG",
        "GPE",
        "LOC",
        "PRODUCT",
        "EVENT",
        "WORK_OF_ART",
        "LAW",
        "NORP",
        "FAC",
    }
    GRAPH_MAX_RELATIONSHIPS: int = 12

    # ── Embeddings (local HuggingFace model) ─────────────
    EMBEDDING_MODEL: str = "sentence-transformers/all-MiniLM-L6-v2"
    EMBEDDING_DIMENSION: int = 384

    # ── ChromaDB ─────────────────────────────────────────
    CHROMA_PERSIST_DIR: str = "./data/chroma_db"

    # ── LLM (HuggingFace Inference API) ──────────────────
    HF_TOKEN: str = os.getenv("HF_TOKEN", "")  # HuggingFace API token (set in .env)
    LLM_MODEL: str = "Qwen/Qwen2.5-72B-Instruct"
    LLM_MAX_NEW_TOKENS: int = 1024
    LLM_TEMPERATURE: float = 0.3
    SUMMARY_MAX_TOKENS: int = 512

    # ── LangSmith Tracing (optional) ─────────────────────
    LANGSMITH_TRACING: bool = False
    LANGSMITH_API_KEY: str = ""
    LANGSMITH_ENDPOINT: str = "https://api.smith.langchain.com"
    LANGSMITH_PROJECT: str = "pdf-assistant-rag"

    # ── Reranker ─────────────────────────────────────────
    RERANKER_MODEL: str = "cross-encoder/ms-marco-MiniLM-L-6-v2"
    # ── Vision / Image captioning ─────────────────────
    VISION_PROVIDER: str | None = None  # e.g. 'openai'
    VISION_MODEL: str | None = None
    OPENAI_API_KEY: str = ""

    # ── Workspace Invitation ─────────────────────────
    APP_URL: str = "http://localhost:3000"
    INVITE_TOKEN_EXPIRY_HOURS: int = 72
    EMAIL_FROM: str = "no-reply@example.com"
    SMTP_HOST: str = ""
    SMTP_PORT: int = 0
    SMTP_USER: str = ""
    SMTP_PASSWORD: str = ""

    @property
    def cors_origins(self) -> list[str]:
        if self.ENVIRONMENT == "production":
            return [o.strip() for o in self.ALLOWED_ORIGINS.split(",")]
        return ["*"]

    class Config:
        env_file = ".env"
        env_file_encoding = "utf-8"
        extra = "ignore"


@lru_cache()
def get_settings() -> Settings:
    """Cached settings instance — loaded once on startup."""
    return Settings()